Conventionally, various types of structures of a substrate unit having a substrate provided therein for causing static electricity to escape from the substrate to a body earth have been proposed.
For example, an on-board electronic device described in Japanese Patent Laying-Open No. 2007-329003 includes a conductive enclosure, a resin case arranged in the enclosure, a control substrate stored in the enclosure and having a conductive pattern formed thereon, a conductive plate in contact with this conductive pattern, and a screw fixing the control substrate and the conductive plate to a boss provided for the resin case.
A game machine described in Japanese Patent Laying-Open No. 2000-37507 includes a substrate box and an attachment assistance member having conductivity to which this substrate box is fixed.
The substrate box includes an upper lid member and a bottom lid member. The substrate is stored between the upper lid member and the bottom lid member.
The bottom lid member has formed thereon a cylindrical first engagement part having a hole formed therein. The upper lid member also has formed thereon a cylindrical second engagement part having a hole formed therein.
The attachment assistance member has a plate shape. The attachment assistance member is provided with a cylindrical conduction assistance member. This conduction assistance member is provided at a portion of the inner surface of the attachment assistance member that is opposite to the first engagement part of the bottom lid member.
The conduction assistance member is fixed with a first screw provided at the outer surface side of the attachment assistance member. The first screw penetrates the attachment assistance member to fix the conduction assistance member to the inner surface of the attachment assistance member.
This conduction assistance member has formed therein a female screw hole extending therethrough in the axial direction. The conduction assistance member is inserted in the hole of the first engagement part of the bottom lid member.
The substrate is fixed to the leading end of the cylindrical conduction assistance member with a second screw. Specifically, the second screw includes a shaft part inserted in the hole of the conduction assistance member and a head part provided on an end of this shaft part. The substrate is held between the head part of the second screw and the leading end of the conduction assistance member. The second screw is inserted from the outside through the hole of the second engagement part. The substrate is electrically connected to the conductive attachment assistance member with the conduction assistance member.
It is noted that the measures against static electricity as described above are not limited to the substrate unit including a circuit substrate or a control substrate, but has also been proposed in various fields.
For example, Japanese Utility Model Laying-Open No. 5-26668 proposes a structure for taking measures against static electricity in a recess of a door trim for vehicle.